Glossary / Exposure limits
Threshold limit value (TLV)
Threshold limit value (TLV) is an occupational exposure guideline published by ACGIH, the American Conference of Governmental Industrial Hygienists. A TLV is the airborne level to which it is believed nearly all workers may be repeatedly exposed, day after day, without adverse health effects, and it is a guideline rather than a law.
Explanation
ACGIH reviews published science each year and updates its TLVs, so they tend to reflect newer research than many OSHA limits. TLVs come in several forms: a TLV-TWA for an 8-hour day, a TLV-STEL for short periods, and a TLV-C ceiling that should not be exceeded. Some carry notations such as skin, meaning absorption through the skin can add substantially to the dose, or sensitizer.
ACGIH is a professional association, not a regulator, so TLVs have no legal force on their own in the United States. They can become enforceable when a rule or a contract adopts them. Many employers adopt TLVs as their company standard, especially where the OSHA Permissible exposure limit (PEL) is older and higher.
The ACGIH publishes TLVs with supporting documentation, and the book is copyrighted and sold, so SDSs list only the values. A supplier may pick TLVs, PELs or both for Section 8. Check which year or edition applies if it matters for compliance.
TLVs are meant for use by trained industrial hygienists. They are not sharp dividing lines between safe and dangerous, and ACGIH stresses that individual susceptibility varies.
What to do and watch for
- Check whether your employer or customer requires TLVs even where OSHA has no PEL.
- Look for skin and sensitizer notations next to the number.
- Compare TLV-TWA, STEL and ceiling values with your monitoring data.
Where it appears on an SDS
- Section 8: Exposure controls / personal protection. Often lists ACGIH TLVs in a table of control parameters, with TWA, STEL or ceiling designations.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.